System and method for providing a loop free topology in a network environment

ABSTRACT

An example method is provided and includes executing an intermediate system to intermediate system (IS-IS) protocol for a first set of network links in a network. The method also includes executing a spanning tree protocol (STP) for a second set of network links, and generating a network topology that includes using a broadcast tree system identifier (ID) as a root bridge ID for the network. The method further includes communicating the root bridge ID to a neighboring network element. In more specific examples, an STP block is communicated to a redundant link, which connects a first switch and a second switch. The first and second switches can converge on the network topology using the broadcast tree system ID.

TECHNICAL FIELD

This disclosure relates in general to the field of communications and,more particularly, to providing a loop free topology in a networkenvironment.

BACKGROUND

Ethernet architectures have grown in complexity in recent years. This isdue, at least in part, to diverse technologies that have emerged toaccommodate a plethora of end users. For example, Data Center Ethernet(DCE) represents an extension to Classical Ethernet (CE), and it canoffer a lower cost, lower latency, high-bandwidth configuration. Theforwarding methodology adopted by DCE networks is generally scalableand, further, provides forwarding paths with equal-cost multipathingwith support for different forwarding topologies. In certain networkscenarios, topology information may not be current, accurate, and/orconsistent. Optimally managing network topologies presents a significantchallenge to system designers, network operators, and service providersalike.

BRIEF DESCRIPTION OF THE DRAWINGS

To provide a more complete understanding of the present disclosure andfeatures and advantages thereof, reference is made to the followingdescription, taken in conjunction with the accompanying figures, whereinlike reference numerals represent like parts, in which:

FIG. 1 is a simplified block diagram of a communication system forproviding a loop free topology in a network environment in accordancewith one embodiment of the present disclosure;

FIG. 2 is a simplified block diagram illustrating additional detailsrelated to the communication system in accordance with one embodiment;

FIG. 3 is a simplified block diagram illustrating details related to apossible example of the communication system in accordance with oneembodiment;

FIG. 4 is a simplified block diagram illustrating details related to apossible example of the communication system in accordance with oneembodiment;

FIG. 5 is a simplified block diagram illustrating details related to apossible example of the communication system in accordance with oneembodiment; and

FIG. 6 is a simplified flowchart illustrating a series of exampleoperations for a flow associated with the communication system.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS Overview

A method is provided in one example embodiment and includes executing anintermediate system to intermediate system (IS-IS) protocol for a firstset of network links in a network. The method also includes executing aspanning tree protocol (STP) for a second set of network links, andgenerating a network topology that includes using a broadcast treesystem identifier (ID) as a root bridge ID for the network. The methodfurther includes communicating the root bridge ID to a neighboringnetwork element. In more specific examples, an STP block is communicatedto a redundant link, which connects a first switch and a second switch.The first and second switches can converge on the network topology usingthe broadcast tree system ID.

In more particular examples, the network includes a Data Center Ethernet(DCE) network and a Classical Ethernet (CE) network, which form alayer-2 (L2) broadcast domain. The broadcast tree system ID can beassociated with the IS-IS protocol, and the root bridge ID is associatedwith the STP. A selected gateway port is configured to receive asuperior Bridge Protocol Data Unit (BPDU), and in response to thesuperior BPDU, the selected port can be placed in a blocked state. Inother embodiments, the broadcast tree system ID is provided as the rootbridge ID per virtual local area network (VLAN), and the broadcast treesystem ID is a Media Access Control address (MAC address).

Example Embodiments

Turning to FIG. 1, FIG. 1 is a simplified block diagram of acommunication system 10 for providing a loop free topology in a networkenvironment in accordance with one embodiment. FIG. 1 may include a DataCenter Ethernet (DCE) network 12, a Classical Ethernet (CE) switch 14and a CE switch 16, which can be coupled together via a communicationlink 15. Additionally, FIG. 1 may include a CE network 18, a set of DCEswitches 20 and 22, along with a set of CE-DCE gateway switches 24 and28.

DCE networks commonly use a routing protocol (e.g., intermediate systemto intermediate system (IS-IS)) for forwarding purposes, where CEnetworks commonly use a spanning tree protocol (STP) as their forwardingprotocol. DCE and CE form the same layer-2 (L2) broadcast domain suchthat a mechanism is needed to avoid the loop that forms acrossinterconnected CE and DCE networks. In the illustration of FIG. 1, DCEswitches 20 and 22 can be executing an IS-IS protocol. Concurrently,CE-DCE switches 24 and 28 can be employing the IS-IS protocol on DCElinks, and using STP on the CE links. In this particular configurationof FIG. 1, CE switch 16 may be executing STP. In regards to the exampleof FIG. 1, a loop could exist, where the path is defined from CE switch16, to CE-DCE switch 24, to DCE switch 20, to DCE switch 22, to CE-DCEswitch 28, to CE switch 14, and then returning back to CE switch 16.

In one particular example, DCE network 12 is representative of a layer 2(L2) multi-pathing (L2MP) network, which may be executing the IS-ISforwarding protocol. DCE network 12 and CE network 18 are associatedwith the same broadcast domain. This could mean, for example, that avirtual local area network (VLAN) associated with CE network 18 can spaninto DCE network 12. Because of their inherent protocols, if a loopoccurs between DCE network 12 and CE network 18, it is not properlyblocked. This is because protocols fail to uniformly evaluate both ofthese networks, as a collective whole.

In order to prevent loops in DCE/CE hybrid networks, communicationsystem 10 can provide an L2 gateway spanning tree protocol (L2G-STP)mechanism and an L2 Gateway Interconnect Protocol (L2GIP) mechanism. Asan overview, L2G-STP can ensure a loop-free CE-DCE L2 domain, whileL2GIP can offer extended capabilities to L2G-STP, as discussed below. Ina general sense, the main functionality of the L2G-STP mechanism is tooffer a segmented spanning tree, whereas the main functionality of theL2GIP mechanism is to build (and to maintain adjacencies) between CE-DCEgateway switches 24 and 28.

Hence, communication system 10 can be employed to prevent loops fromoccurring within networks (and/or clouds) of FIG. 1. More particularly,certain embodiments of communication system 10 can represent DCE network12 as a pseudo bridge, or a virtual switch (as outlined below).Furthermore, embodiments presented herein allow an STP block to be theredundant link between CE switch 16 and CE switch 14. This is commonlyreferred to as the ‘wiring closet’ in switching applications.Communication system 10 allows CE-DCE gateway switches (connected to thesame DCE network) to be represented as a single virtual switch such thatthe STP block port is pushed down. This stands in contrast to blocking acore link, which connects gateway switches. Hence, communication system10 can use a broadcast tree system identifier (e.g., per-VLAN) as theSTP root bridge identifier (ID) on the associated CE-DCE gatewayswitches. This operation would effectively push the STP block tocommunication link 15, which offers redundancy for the system. Thearchitecture of communication system 10 can offer seamlessinteroperability with existing Ethernet switches and end devices.

In terms of advantages, any possible user provisioning for the CE-DCEgateway switches is minimal, when employing the described approach toachieve a virtual switch paradigm. Additionally, such a strategy ispragmatic because it is less prone to errors and, further, because itreduces debugging operations. Moreover, an object is locally derivedusing IS-IS (instead of STP), which explicitly synchronizes the virtualswitch information across CE-DCE gateway switches 24 and 28 in DCEnetwork 12. Note that such a solution is simple to implement and,furthermore, transient loops would be avoided whenever DCE network 12would split, change, or merge with another entity. Details relating tothe possible signaling and interactions between the components ofcommunication system 10 are provided below with reference to FIGS. 2-6.

Note that before turning to the example flows and infrastructure ofexample embodiments of the present disclosure, a brief overview of theswitching environment is provided for purposes of context andexplanation. Link state routing is a protocol that allows a node in anetwork to determine network topology by sharing information about atransmission cost to each of its neighboring nodes. Link state routingpackets are transmitted to (and received from) neighbors. The leastexpensive path to various destinations can be determined using the linkstate information. Link state information can be used to generatenetwork topology information at various network nodes for creatingforwarding tables. The forwarding tables allow network nodes (such asswitches and bridges) to forward the received traffic on an appropriateoutput interface. In order to generate a network topology map and aforwarding table at a specific node, link state information isdistributed from various network nodes. Each network node is configuredto create a link state packet having information about the distance,delay, or cost to each of its neighbors. A link state record (LSR) canthen be transmitted to neighboring nodes.

Transient loops arise when network topology changes because neighboringnodes may not be forwarding transmissions using the same generatednetwork topology. Transient and permanent loops waste network bandwidthand, further, may burden end nodes with duplicate copies of topologyinformation. One mechanism for preventing loops is STP. STP commonlyruns on a switch and, further, operates to maintain a loop-free topologyin an L2 switched network. The term spanning tree protocol (STP) as usedherein includes any version of STP, including for example, traditionalSTP (IEEE 802.1d), rapid spanning tree protocol (RSTP) (IEEE 802.1w),multiple spanning tree protocol (MSTP) (IEEE 802.1s), or any otherspanning tree protocol. CE switches may use STP to prevent loops,whereas other devices such as DCE switches may be configured to useprotocols other than STP (e.g., IS-IS) to provide loop-free operations.While STP and other protocols work well for a standalone networkcomprising switches that utilize only one protocol for preventing loops,the different protocols may not interoperate with each other and,therefore, cannot effectively be used in a combined (i.e., a hybrid)network.

FIG. 1 depicts clouds that form a switching network, where a cloud isdefined as a set of one of more network switches/bridges and end hosts:all of which may be interconnected. At the edge of a DCE cloud and a CEcloud, a model for control plane interaction between the two clouds iscommonly defined. Specifically, DCE and CE use different protocols toconstruct their respective forwarding topology (IS-IS versus STP). Thus,even though a single L2 broadcast domain would span the clouds, twodifferent protocols govern the determination of the forwarding topology.This is especially important for the behavior of broadcast traffic(e.g., frames with an unknown Media Access Control address (MAC address)address are flooded using broadcast throughout the network). Theinconsistency in topology creates an opportunity for problematic loopsto develop. One immediate issue surfaces as to which of the two clouds(DCE or CE) has the responsibility to detect and to break the loops inthe broadcast domain.

In certain embodiments, communication system 10 interoperates with STPat the CE cloud level and interacts with IS-IS in an interlock manner atthe DCE cloud level to prevent transient loops. Operationally, CE-DCEgateway switches 24 and 28 can be configured to send out the same STProot bridge ID. Stated in different terminology, CE-DCE gateway switches24 and 28 can virtualize the STP root inside the DCE network. In morespecific implementations, the STP mechanism being executed on CE-DCEgateway switches 24 and 28 can use the IS-IS broadcast tree system ID(which may be operating on the DCE links) as the STP root bridge ID.Certain routing protocols (e.g., IS-IS) provide that gateway switches 24and 28 (after IS-IS converges) should derive their topology at the sameroot switch (and, therefore, the same system ID). STP on both gatewayswitches 24 and 28 can advertise the same STP root bridge ID and, hence,the STP block can be pushed down to a redundant link 15, which connectsCE switch 16 and CE switch 14 (i.e., the wiring closet).

In a general sense, the STP being executed on a given CE-DCE gatewayswitch uniformly enforces the STP root that is within DCE network 12.Further, communication system 10 can prevent a loop by enforcing the STPbeing executed on CE-DCE gateway switches 24 and 28 in order to blockthe port when it receives a superior STP Bridge Protocol Data Unit(BPDU) from CE network 12. Hence, in an example of FIG. 1, CE-DCEgateway switches 24 and 28 can block the link between gateway switch 24and CE switch 16 (or between gateway switch 28 and CE switch 14) if theyreceive a superior BPDU from CE switch 16, or from CE switch 14. Such anoperation could effectively prevent the CE-DCE L2 network loops. Thenotion is to uniformly enforce that STP root that is within DCE network12.

A given gateway that has connectivity to both CE network 18 and DCEnetwork 12 can be referred to as an L2 gateway switch. In essence, suchswitches should use the same information in their STP BPDUs. In thissense, the gateway switches (connected to both networks) would view DCEnetwork 12 as a virtual switch. In one particular example, communicationsystem 10 can be provisioned to leverage the IS-IS broadcast tree systemID (e.g., per-VLAN) as the STP root bridge ID on CE-DCE gateway switches24 and 28. For example, the MAC address of the broadcast tree can beused by CE-DCE gateway switches 24 and 28. In using such a mechanism,the gateway switches that are executing the IS-IS protocol wouldeventually converge at one root system ID (e.g., one broadcast tree ID,one root MAC address, etc.). Hence, all the gateway switches wouldcommunicate BPDUs with the same root bridge ID. This allows the networkto represent DCE network 12 as a single switch. Before turning to someof the additional operations of this architecture, a brief discussion isprovided about some of the infrastructure of the architecture, which isdepicted by FIG. 2.

FIG. 2 is a simplified block diagram illustrating potential detailsassociated with communication system 10. In this particular example,CE-DCE gateway switches 24 and 28 include a respective processor 36 a-b,a respective memory element 38 a-b, a respective L2GIP module 30 a-b, arespective L2G-STP module 32 a-b, and respective routing modules 34 a-b(e.g., IS-IS routing modules). Also included in FIG. 2 is a dashed line40, which depicts L2GIP adjacency being built between CE-DCE gatewayswitches 24 and 28 (e.g., using an IS-IS protocol). Note also that L2GIPmodules 30 a-b may readily be incorporated into respective L2G-STPmodules 32 a-b in different embodiments (or vice versa), or routingmodules 34 a-b can be part of hybrid configurations in which any of themodules of FIG. 2 are suitable consolidated, combined, etc.

DCE network 12 and CE network 18 represent a series of points or nodesof interconnected communication paths for receiving and transmittingpackets of information that propagate through communication system 10.These networks offer a communicative interface between network elements(e.g., switches, bridges, gateways, etc.) and may be any IP network,local area network (LAN), virtual LAN (VLAN), wireless LAN (WLAN),metropolitan area network (MAN), wide area network (WAN), extranet,Intranet, virtual private network (VPN), or any other appropriatearchitecture or system that facilitates communications in a networkenvironment. The networks can support a transmission control protocol(TCP)/IP, or a user datagram protocol (UDP)/IP in particular embodimentsof the present disclosure; however, these networks may alternativelyimplement any other suitable communication protocol for transmitting andreceiving data packets within communication system 10.

DCE switches 20, 22 and CE-DCE gateway switches 24, 28 are networkelements that route (or that cooperate with each other in order toroute) traffic and/or packets in a network environment. As used hereinin this Specification, the term ‘network element’ is meant to encompassswitches, routers, gateways, bridges, loadbalancers, firewalls, inlineservice nodes, proxies, servers, processors, modules, or any othersuitable device, component, element, or object operable to exchangeinformation in a network environment. This network element may includeany suitable hardware, software, components, modules, interfaces, orobjects that facilitate the operations thereof. This may be inclusive ofappropriate algorithms and communication protocols that allow for theeffective exchange (reception and/or transmission) of data orinformation. DCE switches 20 and 22 are L2MP core switches in oneparticular example. At a point in time, DCE switches 20 and 22, alongwith CE-DCE gateway switches 24 and 28, converge at one IS-IS broadcasttree. CE-DCE gateway switches 24 and 28 can share the same perspectiveof the network via STP BPDUs.

In operation, L2G-STP modules 32 a-b are configured to terminate an STPinstance at respective CE-DCE gateway switches 24 and 28. L2G-STPdefines the ports to be provided in one of the following L2 gateway porttypes: a backbone gateway port (i.e., default gateway port type), and anuplink gateway port. Switches commonly have a priority list, which canbe influenced by configuration, updates, information from its peers,etc. Upon receiving a superior BPDU, a given switch can compare itslocal priority list to this received information.

DCE addressing and forwarding can include the use of a locally assignedaggregatable (or hierarchical) MAC address for forwarding activities.Edge switches can maintain a mapping between the classical MAC addressand the corresponding hierarchical MAC address. The mapping can beestablished via learning between the network elements, where use of aMAC-in-MAC header can be employed to carry the hierarchical MAC addressacross the DCE network. A link state protocol can be used to determinethe forwarding topology and, further, to support shortest path and equalcost multi-path forwarding for unicast traffic. Multicast frames canalso readily use multi-pathing, albeit using a slightly differentscheme. Additionally, a single control protocol can be used to computeunicast paths, multicast path, and broadcast distribution trees.

For the L2G-STP mechanism, and in regards to the backbone gateway port,the STP root backbone inside the DCE cloud is enforced. The backbonegateway port can ensure that it is consistently designated as thesuperior port. [Note that a backbone network or network backbone iscommonly a part of computer network infrastructure that interconnectsvarious pieces of network: providing a path for the exchange ofinformation between different LANs or sub-networks. A backbone can tietogether diverse networks in the same building, in different buildingsin a campus environment, over wide areas, etc. Normally, the backbone'scapacity is greater than the networks connected to it.] In cases wherethe backbone gateway port receives a superior STP BPDU, the architecturewill respond by placing the port in a gateway port inconsistency blockedstate. For the uplink gateway port, the L2G-STP mechanism allows the STProot to be outside the DCE network. In using an auto-detection approach,when receiving superior BPDUs, the backbone port type can transition toan uplink port type. In addition, for an explicit configuration of theuplink port type approach, the uplink gateway port can ensure that it isnot the designated superior port. Hence, if the uplink gateway portreceived an inferior STP BPDU, then the architecture would respond byputting the port in an uplink gateway port inconsistency blocked state.

Note that DCE switches 20, 22 and CE-DCE gateway switches 24, 28 mayshare (or coordinate) certain processing operations. Using a similarrationale, their respective memory elements may store, maintain, and/orupdate data in any number of possible manners. In a general sense, thearrangement depicted in FIG. 2 may be more logical in itsrepresentations, whereas a physical architecture may include variouspermutations/combinations/hybrids of these elements. In one exampleimplementation, CE-DCE gateway switches 24, 28 include software (e.g.,as part of L2GIP modules 30 a-b and/or L2G-STP modules 32 a-b) toachieve the switching operations, as outlined herein in this document.In other embodiments, this feature may be provided externally to any ofthe aforementioned elements, or included in some other network elementto achieve this intended functionality. Alternatively, several elementsmay include software (or reciprocating software) that can coordinate inorder to achieve the operations, as outlined herein. In still otherembodiments, any of the devices of FIGS. 1-5 may include any suitablealgorithms, hardware, software, components, modules, interfaces, orobjects that facilitate these switching operations.

FIG. 3 is a simplified block diagram illustrating one example of asegmented spanning tree system 50. FIGS. 3-5 can assist in explaining anexample flow for particular switching events and, therefore, theseillustrations are discussed together. FIG. 3 includes a set of DCEnetworks 52 and 54, which include a set of switches and gateways forpropagating information in a network environment. Note that each switchgroup belongs to the same domain. In this particular example, anassumption is made that the STP root is inside the DCE cloud. A givenswitch (e.g., switch #12) can terminate the STP data, as shown by anelement 58. In addition, a peer switch (e.g., switch #13) can receive asuperior BPDU from switch #12. This is illustrated by an element 60 ofFIG. 3. In addition, switch #22 can receive a superior BPDU from switch#13, as is depicted by an element 62.

In regards to the possible advantages associated with a segmentedspanning tree, there is virtually no configuration obligation.Furthermore, there is a smaller, more manageable sized STP in the CEclouds. Such a strategy can also achieve a rapid convergence. Notopology change (TC) is needed across the DCE, and there is no STPmechanism or L2GIP required inside the DCE network. Moreover, such anapproach avoids concerns about DCE cloud merging, splitting, changing,etc.

Such a segmented spanning tree approach may present certain challenges.For example, the STP block typically is provided at the DCE-CE gatewayswitch port. It is desirable to utilize a high-bandwidth CE-DCE gatewaylink, and have the redundant link blocked in the CE wiring closet.Moreover, such an approach may not provide connectivity between DCEclouds using CE. To resolve the issue associated with utilizing CE-DCElinks, a locally derived common root bridge ID can be employed. Exampleoperations associated with the common root bridge ID are detailed belowwith reference to FIG. 4.

FIG. 4 is a simplified block diagram illustrating another example of asegmented spanning tree system 70. In this particular example, a DCEnetwork 72 is provided with a number of switches and gateways fordirecting network traffic. Each of the switches use the IS-IS broadcasttree system such that information being exchanged between the gatewayswitches is similar. An element 74 represents the notion of utilizinghigh bandwidth core links in this example. Note that a link betweenswitch #13 and switch #15 has been blocked in this scenario. This blockis problematic because it represents a core link being blocked, whichinhibits an optimal bandwidth usage. Furthermore, an element 76 isprovided to illustrate that switch #13 receives a superior BPDU fromswitch #12. The link between switch #14 and switch #15 is also blocked,where this link is representative of the wiring closet. This link isgenerally provided for redundancy purposes. Ideally, any block should bepushed to this link (i.e., to the wiring closet).

FIG. 5 is a simplified block diagram illustrating example activitiesassociated with segmented spanning tree system 70. This particularillustration is reflective of a locally derived common root bridge ID.Note that there is a better bridge priority in the CE cloud (e.g., ifswitch #9 were used instead of switch #15, this would be deemed as amisconfiguration). FIG. 5 also illustrates a set of BPDUs 84 and 86. Inregards to BPDU 84, the following parameters are configured: RootBID=R10, Root Path Cost=0, and a Designated BID=S12. More specifically,for the root bridge ID, the bridge priority default value is given as8192. The system ID is locally derived, and the MAC address is locallyderived from the DCE IS-IS broadcast tree root system ID. For BPDU 86,the following parameters are configured: Root BID=R10, Root Path Cost=0,and a Designated BID=S13. In terms of the root bridge ID, the bridgepriority has a default value of 8192. In addition, the system ID islocally derived, and the MAC address is locally derived from the DCEIS-IS broadcast tree root system ID.

In operation, each gateway switch locally derives a common root bridgeID. The bridge priority field (e.g., 4 bits) of the common root bridgeID can employ administrative control to relocate the STP root. In termsof how a given gateway switch would understand the configured rootbridge priority value, there are several possible approaches. In a firstapproach, a better bridge priority is adapted from the received BPDUs inthe case where the MAC address component of the root bridge ID presentsa match. In a second approach, a new LSP TLV can be employed topropagate the incremental bridge priority changes.

Such an approach provides the capability to select CE-DCE core links,while pushing the redundant link block down into a CE wiring closet.However, such a strategy may not provide optimal connectivity betweenDCE clouds via the CE cloud. Furthermore, such a strategy would not havethe STP root outside the DCE. To resolve the DCE cloud connectivityissue via the CE and/or to address the STP root outside of DCE, theL2GIP protocol can be used.

Turning to FIG. 6, FIG. 6 is a simplified flowchart illustrating oneexample scenario 100 that could be accommodated by communication system10. The flowchart may begin at 110, where there is a detection of agateway port, which serves as a first trigger. The typically happenswhen the first port is up on the CE side of a particular VLAN, and onthe L2MP side. This would essentially allow the VLAN to operate as atraffic gateway. At 120, the IS-IS broadcast tree system ID is used as aroot bridge ID to develop a proper network topology. At 130, the rootbridge ID is communicated to a neighboring network element. At 140, byenforcing the STP being executed on CE-DCE gateway switches, when asuperior STP BPDU is received, the port is blocked (which caneffectively block particular links between gateway switches, CEswitches, etc.). At 150, the gateway switches that are executing theIS-IS protocol would eventually converge at one root system ID (e.g.,one broadcast tree ID, one root MAC address, etc.). Hence, all thegateway switches would communicate BPDUs with the same root bridge ID.

Note that in certain example implementations, the switching functionsoutlined herein may be implemented by logic encoded in one or moretangible media (e.g., embedded logic provided in an application specificintegrated circuit (ASIC), digital signal processor (DSP) instructions,software (potentially inclusive of object code and source code) to beexecuted by a processor, or other similar machine, etc.). In some ofthese instances, a memory element (as shown in FIG. 2) can store dataused for the operations described herein. This includes the memoryelement being able to store software, logic, code, or processorinstructions that can be executed to carry out the activities describedin this Specification. A processor can execute any type of instructionsassociated with the data to achieve the operations detailed herein inthis Specification. In one example, the processor (as shown in FIG. 2)could transform an element or an article (e.g., data) from one state orthing to another state or thing. In another example, the activitiesoutlined herein may be implemented with fixed logic or programmablelogic (e.g., software/computer instructions executed by a processor) andthe elements identified herein could be some type of a programmableprocessor, programmable digital logic (e.g., a field programmable gatearray (FPGA), an erasable programmable read only memory (EPROM), anelectrically erasable programmable ROM (EEPROM)) or an ASIC thatincludes digital logic, software, code, electronic instructions, or anysuitable combination thereof.

In one example implementation, L2GIP modules 30 a-b and/or L2G-STPmodules 32 a-b include software in order to achieve the switchingfunctions outlined herein. These activities can be facilitated by CE-DCEswitches 24, 28 and/or any of the elements of FIGS. 1-5. CE-DCE switches24, 28 can include memory elements for storing information to be used inachieving the intelligent switching control, as outlined herein.Additionally, CE-DCE switches 24, 28 may include a processor that canexecute software or an algorithm to perform the switching activities, asdiscussed in this Specification. These devices may further keepinformation in any suitable memory element (random access memory (RAM),ROM, EPROM, EEPROM, ASIC, etc.), software, hardware, or in any othersuitable component, device, element, or object where appropriate andbased on particular needs. Any possible memory items (e.g., database,table, cache, etc.) should be construed as being encompassed within thebroad term ‘memory element.’ Similarly, any of the potential processingelements, modules, and machines described in this Specification shouldbe construed as being encompassed within the broad term ‘processor.’

Note that with the examples provided herein, interaction may bedescribed in terms of two or three elements. However, this has been donefor purposes of clarity and example only. In certain cases, it may beeasier to describe one or more of the functionalities of a given set offlows by only referencing a limited number of network elements. Itshould be appreciated that communication system 10 (and its teachings)are readily scalable and can accommodate a large number of clouds,networks, and/or switches, as well as more complicated/sophisticatedarrangements and configurations. Accordingly, the examples providedherein should not limit the scope or inhibit the broad teachings ofcommunication system 10 as potentially applied to a myriad of otherarchitectures. Additionally, although described with reference toparticular scenarios where L2GIP modules 30 a-b, L2G-STP modules 32 a-b,and/or routing modules 34 a-b are provided separately, these modules canbe consolidated or combined in any suitable fashion, or provided in asingle proprietary unit.

It is also important to note that the operations discussed withreference to FIGS. 1-6 illustrate only some of the possible scenariosthat may be executed by, or within, communication system 10. Some ofthese operations may be deleted or removed where appropriate, or thesesteps may be modified or changed considerably without departing from thescope of the present disclosure. In addition, a number of theseoperations have been described as being executed concurrently with, orin parallel to, one or more additional operations. However, the timingof these operations may be altered considerably. The precedingoperational flows have been offered for purposes of example anddiscussion. Substantial flexibility is provided by communication system10 in that any suitable arrangements, chronologies, configurations, andtiming mechanisms may be provided without departing from the teachingsof the present disclosure.

Although the present disclosure has been described in detail withreference to particular embodiments, it should be understood thatvarious other changes, substitutions, and alterations may be made heretowithout departing from the spirit and scope of the present disclosure.For example, although the present disclosure has been described asoperating in conferencing environments or arrangements, the presentdisclosure may be used in any communications environment that couldbenefit from such technology. Virtually any configuration that seeks tointelligently switch packets could enjoy the benefits of the presentdisclosure. Numerous other changes, substitutions, variations,alterations, and modifications may be ascertained to one skilled in theart and it is intended that the present disclosure encompass all suchchanges, substitutions, variations, alterations, and modifications asfalling within the scope of the appended claims.

1. A method, comprising: executing an intermediate system tointermediate system (IS-IS) protocol for a first set of network links ina network; executing a spanning tree protocol (STP) for a second set ofnetwork links; generating a network topology that includes using abroadcast tree system identifier (ID) as a root bridge ID for thenetwork; and communicating the root bridge ID to a neighboring networkelement.
 2. The method of claim 1, wherein an STP block is communicatedto a redundant link, which connects a first switch and a second switch,and wherein the first and second switches converge on the networktopology using the broadcast tree system ID.
 3. The method of claim 1,wherein the network includes a Data Center Ethernet (DCE) network and aClassical Ethernet (CE) network, which form a layer-2 (L2) broadcastdomain.
 4. The method of claim 1, wherein the broadcast tree system IDis associated with the IS-IS protocol, and the root bridge ID isassociated with the STP.
 5. The method of claim 1, wherein a selectedgateway port is configured to receive a superior Bridge Protocol DataUnit (BPDU), and in response to the superior BPDU, the selected port isplaced in a blocked state.
 6. The method of claim 1, wherein anauto-detection mechanism is utilized to transition to an uplink porttype in response to receiving a superior BPDU.
 7. The method of claim 1,wherein the broadcast tree system ID is provided as the root bridge IDper virtual local area network (VLAN), and wherein the broadcast treesystem ID is a Media Access Control address (MAC address).
 8. Logicencoded in one or more tangible media that includes code for executionand when executed by a processor operable to perform operationscomprising: executing an intermediate system to intermediate system(IS-IS) protocol for a first set of network links in a network;executing a spanning tree protocol (STP) for a second set of networklinks; generating a network topology that includes using a broadcasttree system identifier (ID) as a root bridge ID for the network; andcommunicating the root bridge ID to a neighboring network element. 9.The logic of claim 8, wherein an STP block is communicated to aredundant link, which connects a first switch and a second switch, andwherein the first and second switches converge on the network topologyusing the broadcast tree system ID.
 10. The logic of claim 8, whereinthe network includes a Data Center Ethernet (DCE) network and aClassical Ethernet (CE) network, which form a layer-2 (L2) broadcastdomain.
 11. The logic of claim 8, wherein the broadcast tree system IDis associated with the IS-IS protocol, and the root bridge ID isassociated with the STP.
 12. The logic of claim 8, wherein a selectedgateway port is configured to receive a superior Bridge Protocol DataUnit (BPDU), and in response to the superior BPDU, the selected port isplaced in a blocked state.
 13. The logic of claim 8, wherein anauto-detection mechanism is utilized to transition to an uplink porttype in response to receiving a superior BPDU.
 14. The logic of claim 8,wherein the broadcast tree system ID is provided as the root bridge IDper virtual local area network (VLAN), and wherein the broadcast treesystem ID is a Media Access Control address (MAC address).
 15. Anapparatus, comprising: a memory element configured to store electroniccode, a processor operable to execute instructions associated with theelectronic code, and a layer-2 (L2) gateway-spanning tree protocol(L2G-STP) module configured to interface with the processor and thememory element in order to cause the apparatus to: execute anintermediate system to intermediate system (IS-IS) protocol for a firstset of network links in a network; execute a spanning tree protocol(STP) for a second set of network links; generate a network topologythat includes using a broadcast tree system identifier (ID) as a rootbridge ID for the network; and communicate the root bridge ID to aneighboring network element.
 16. The apparatus of claim 15, wherein anSTP block is communicated to a redundant link, which connects a firstswitch and a second switch, and wherein the first and second switchesconverge on the network topology using the broadcast tree system ID. 17.The apparatus of claim 15 wherein the network includes a Data CenterEthernet (DCE) network and a Classical Ethernet (CE) network, which forma layer-2 (L2) broadcast domain.
 18. The apparatus of claim 15, whereinthe broadcast tree system ID is associated with the IS-IS protocol, andthe root bridge ID is associated with the STP.
 19. The apparatus ofclaim 15, wherein an auto-detection mechanism is utilized to transitionto an uplink port type in response to receiving a superior BPDU.
 20. Theapparatus of claim 15, wherein the broadcast tree system ID is providedas the root bridge ID per virtual local area network (VLAN), and whereinthe broadcast tree system ID is a Media Access Control address (MACaddress).